// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.AspNetCore.Razor.Language.Components;
using Microsoft.AspNetCore.Razor.Language.Legacy;
using Microsoft.AspNetCore.Razor.Language.Syntax;

namespace Microsoft.AspNetCore.Razor.Language
{
    internal class DefaultRazorTagHelperBinderPhase : RazorEnginePhaseBase, IRazorTagHelperBinderPhase
    {
        protected override void ExecuteCore(RazorCodeDocument codeDocument)
        {
            var syntaxTree = codeDocument.GetSyntaxTree();
            ThrowForMissingDocumentDependency(syntaxTree);

            var descriptors = codeDocument.GetTagHelpers();
            if (descriptors == null)
            {
                var feature = Engine.GetFeature<ITagHelperFeature>();
                if (feature == null)
                {
                    // No feature, nothing to do.
                    return;
                }

                descriptors = feature.GetDescriptors();
            }

            var parserOptions = codeDocument.GetParserOptions();

            // We need to find directives in all of the *imports* as well as in the main razor file
            //
            // The imports come logically before the main razor file and are in the order they
            // should be processed.
            DirectiveVisitor visitor;
            if (FileKinds.IsComponent(codeDocument.GetFileKind()) &&
                (parserOptions == null || parserOptions.FeatureFlags.AllowComponentFileKind))
            {
                codeDocument.TryComputeNamespace(fallbackToRootNamespace: true, out var currentNamespace);
                visitor = new ComponentDirectiveVisitor(codeDocument.Source.FilePath, descriptors, currentNamespace);
            }
            else
            {
                visitor = new TagHelperDirectiveVisitor(descriptors);
            }
            var imports = codeDocument.GetImportSyntaxTrees();
            if (imports != null)
            {
                for (var i = 0; i < imports.Count; i++)
                {
                    var import = imports[i];
                    visitor.Visit(import);
                }
            }

            visitor.Visit(syntaxTree);

            // This will always be null for a component document.
            var tagHelperPrefix = visitor.TagHelperPrefix;

            descriptors = visitor.Matches.ToArray();

            var context = TagHelperDocumentContext.Create(tagHelperPrefix, descriptors);
            codeDocument.SetTagHelperContext(context);

            if (descriptors.Count == 0)
            {
                // No descriptors, no-op.
                return;
            }

            var rewrittenSyntaxTree = TagHelperParseTreeRewriter.Rewrite(syntaxTree, tagHelperPrefix, descriptors);

            codeDocument.SetSyntaxTree(rewrittenSyntaxTree);
        }

        private static bool MatchesDirective(TagHelperDescriptor descriptor, string typePattern, string assemblyName)
        {
            if (!string.Equals(descriptor.AssemblyName, assemblyName, StringComparison.Ordinal))
            {
                return false;
            }

            if (typePattern.EndsWith("*", StringComparison.Ordinal))
            {
                if (typePattern.Length == 1)
                {
                    // TypePattern is "*".
                    return true;
                }

               return new StringSegment(descriptor.Name).StartsWith(new StringSegment(typePattern, 0, typePattern.Length - 1), StringComparison.Ordinal);
            }

            return string.Equals(descriptor.Name, typePattern, StringComparison.Ordinal);
        }

        internal abstract class DirectiveVisitor : SyntaxWalker
        {
            public abstract HashSet<TagHelperDescriptor> Matches { get; }

            public abstract string TagHelperPrefix { get; }

            public abstract void Visit(RazorSyntaxTree tree);
        }

        internal sealed class TagHelperDirectiveVisitor : DirectiveVisitor
        {
            private readonly List<TagHelperDescriptor> _tagHelpers;
            private string _tagHelperPrefix;

            public TagHelperDirectiveVisitor(IReadOnlyList<TagHelperDescriptor> tagHelpers)
            {
                // We don't want to consider components in a view document.
                _tagHelpers = new();
                for (var i = 0; i < tagHelpers.Count; i++)
                {
                    var tagHelper = tagHelpers[i];
                    if (!tagHelper.IsAnyComponentDocumentTagHelper())
                    {
                        _tagHelpers.Add(tagHelper);
                    }
                }
            }

            public override string TagHelperPrefix => _tagHelperPrefix;

            public override HashSet<TagHelperDescriptor> Matches { get; } = new HashSet<TagHelperDescriptor>();

            public override void Visit(RazorSyntaxTree tree)
            {
                Visit(tree.Root);
            }

            public override void VisitRazorDirective(RazorDirectiveSyntax node)
            {
                var descendantLiterals = node.DescendantNodes();
                foreach (var child in descendantLiterals)
                {
                    if (!(child is CSharpStatementLiteralSyntax literal))
                    {
                        continue;
                    }

                    var context = literal.GetSpanContext();
                    if (context == null)
                    {
                        // We can't find a chunk generator.
                        continue;
                    }
                    else if (context.ChunkGenerator is AddTagHelperChunkGenerator addTagHelper)
                    {
                        if (addTagHelper.AssemblyName == null)
                        {
                            // Skip this one, it's an error
                            continue;
                        }

                        if (!AssemblyContainsTagHelpers(addTagHelper.AssemblyName, _tagHelpers))
                        {
                            // No tag helpers in the assembly.
                            continue;
                        }

                        for (var i = 0; i < _tagHelpers.Count; i++)
                        {
                            var tagHelper = _tagHelpers[i];
                            if (MatchesDirective(tagHelper, addTagHelper.TypePattern, addTagHelper.AssemblyName))
                            {
                                Matches.Add(tagHelper);
                            }
                        }
                    }
                    else if (context.ChunkGenerator is RemoveTagHelperChunkGenerator removeTagHelper)
                    {
                        if (removeTagHelper.AssemblyName == null)
                        {
                            // Skip this one, it's an error
                            continue;
                        }


                        if (!AssemblyContainsTagHelpers(removeTagHelper.AssemblyName, _tagHelpers))
                        {
                            // No tag helpers in the assembly.
                            continue;
                        }

                        for (var i = 0; i < _tagHelpers.Count; i++)
                        {
                            var tagHelper = _tagHelpers[i];
                            if (MatchesDirective(tagHelper, removeTagHelper.TypePattern, removeTagHelper.AssemblyName))
                            {
                                Matches.Remove(tagHelper);
                            }
                        }
                    }
                    else if (context.ChunkGenerator is TagHelperPrefixDirectiveChunkGenerator tagHelperPrefix)
                    {
                        if (!string.IsNullOrEmpty(tagHelperPrefix.DirectiveText))
                        {
                            // We only expect to see a single one of these per file, but that's enforced at another level.
                            _tagHelperPrefix = tagHelperPrefix.DirectiveText;
                        }
                    }
                }
            }

            private bool AssemblyContainsTagHelpers(string assemblyName, IReadOnlyList<TagHelperDescriptor> tagHelpers)
            {
                for (var i = 0; i < tagHelpers.Count; i++)
                {
                    if (string.Equals(tagHelpers[i].AssemblyName, assemblyName, StringComparison.Ordinal))
                    {
                        return true;
                    }
                }

                return false;
            }
        }

        internal sealed class ComponentDirectiveVisitor : DirectiveVisitor
        {
            private readonly List<TagHelperDescriptor> _notFullyQualifiedComponents;
            private string _filePath;
            private RazorSourceDocument _source;

            public ComponentDirectiveVisitor(string filePath, IReadOnlyList<TagHelperDescriptor> tagHelpers, string currentNamespace)
            {
                _filePath = filePath;

                for (var i = 0; i < tagHelpers.Count; i++)
                {
                    var tagHelper = tagHelpers[i];
                    // We don't want to consider non-component tag helpers in a component document.
                    if (!tagHelper.IsAnyComponentDocumentTagHelper() || IsTagHelperFromMangledClass(tagHelper))
                    {
                        continue;
                    }

                    if (tagHelper.IsComponentFullyQualifiedNameMatch())
                    {
                        // If the component descriptor matches for a fully qualified name, using directives shouldn't matter.
                        Matches.Add(tagHelper);
                        continue;
                    }

                    _notFullyQualifiedComponents ??= new();
                    _notFullyQualifiedComponents.Add(tagHelper);

                    if (currentNamespace is null)
                    {
                        continue;
                    }

                    if (tagHelper.IsChildContentTagHelper())
                    {
                        // If this is a child content tag helper, we want to add it if it's original type is in scope.
                        // E.g, if the type name is `Test.MyComponent.ChildContent`, we want to add it if `Test.MyComponent` is in scope.
                        TrySplitNamespaceAndType(tagHelper, out var typeNamespace);
                        if (!typeNamespace.IsEmpty && IsTypeInScope(typeNamespace, currentNamespace))
                        {
                            Matches.Add(tagHelper);
                        }
                    }
                    else if (IsTypeInScope(tagHelper, currentNamespace))
                    {
                        // Also, if the type is already in scope of the document's namespace, using isn't necessary.
                        Matches.Add(tagHelper);
                    }
                }
            }

            public override HashSet<TagHelperDescriptor> Matches { get; } = new HashSet<TagHelperDescriptor>();

            // There is no support for tag helper prefix in component documents.
            public override string TagHelperPrefix => null;

            public override void Visit(RazorSyntaxTree tree)
            {
                _source = tree.Source;
                Visit(tree.Root);
            }

            public override void VisitRazorDirective(RazorDirectiveSyntax node)
            {
                var descendantLiterals = node.DescendantNodes();
                foreach (var child in descendantLiterals)
                {
                    if (child is not CSharpStatementLiteralSyntax literal)
                    {
                        continue;
                    }

                    var context = literal.GetSpanContext();
                    if (context == null)
                    {
                        // We can't find a chunk generator.
                        continue;
                    }
                    else if (context.ChunkGenerator is AddTagHelperChunkGenerator addTagHelper)
                    {
                        // Make sure this node exists in the file we're parsing and not in its imports.
                        if (_filePath.Equals(_source.FilePath, StringComparison.Ordinal))
                        {
                            addTagHelper.Diagnostics.Add(
                                ComponentDiagnosticFactory.Create_UnsupportedTagHelperDirective(node.GetSourceSpan(_source)));
                        }
                    }
                    else if (context.ChunkGenerator is RemoveTagHelperChunkGenerator removeTagHelper)
                    {
                        // Make sure this node exists in the file we're parsing and not in its imports.
                        if (_filePath.Equals(_source.FilePath, StringComparison.Ordinal))
                        {
                            removeTagHelper.Diagnostics.Add(
                                ComponentDiagnosticFactory.Create_UnsupportedTagHelperDirective(node.GetSourceSpan(_source)));
                        }
                    }
                    else if (context.ChunkGenerator is TagHelperPrefixDirectiveChunkGenerator tagHelperPrefix)
                    {
                        // Make sure this node exists in the file we're parsing and not in its imports.
                        if (_filePath.Equals(_source.FilePath, StringComparison.Ordinal))
                        {
                            tagHelperPrefix.Diagnostics.Add(
                                ComponentDiagnosticFactory.Create_UnsupportedTagHelperDirective(node.GetSourceSpan(_source)));
                        }
                    }
                    else if (context.ChunkGenerator is AddImportChunkGenerator usingStatement && !usingStatement.IsStatic)
                    {
                        // Get the namespace from the using statement.
                        var @namespace = usingStatement.ParsedNamespace;
                        if (@namespace.IndexOf('=') != -1)
                        {
                            // We don't support usings with alias.
                            continue;
                        }

                        for (var i = 0; _notFullyQualifiedComponents is not null && i < _notFullyQualifiedComponents.Count; i++)
                        {
                            var tagHelper = _notFullyQualifiedComponents[i];
                            Debug.Assert(!tagHelper.IsComponentFullyQualifiedNameMatch(), "We've already processed these.");

                            if (tagHelper.IsChildContentTagHelper())
                            {
                                // If this is a child content tag helper, we want to add it if it's original type is in scope of the given namespace.
                                // E.g, if the type name is `Test.MyComponent.ChildContent`, we want to add it if `Test.MyComponent` is in this namespace.
                                TrySplitNamespaceAndType(tagHelper, out var typeName);
                                if (!typeName.IsEmpty && IsTypeInNamespace(typeName, @namespace))
                                {
                                    Matches.Add(tagHelper);
                                }
                            }
                            else if (IsTypeInNamespace(tagHelper, @namespace))
                            {
                                // If the type is at the top-level or if the type's namespace matches the using's namespace, add it.
                                Matches.Add(tagHelper);
                            }
                        }
                    }
                }
            }

            internal static bool IsTypeInNamespace(StringSegment typeName, string @namespace)
            {
                if (!TrySplitNamespaceAndType(typeName, out var typeNamespace, out var _) || typeNamespace.IsEmpty)
                {
                    // Either the typeName is not the full type name or this type is at the top level.
                    return true;
                }

                return typeNamespace.Equals(@namespace, StringComparison.Ordinal);
            }

            internal static bool IsTypeInNamespace(TagHelperDescriptor tagHelper, string @namespace)
            {
                if (!TrySplitNamespaceAndType(tagHelper, out var typeNamespace) || typeNamespace.IsEmpty)
                {
                    // Either the typeName is not the full type name or this type is at the top level.
                    return true;
                }

                return typeNamespace.Equals(@namespace, StringComparison.Ordinal);
            }

            // Check if the given type is already in scope given the namespace of the current document.
            // E.g,
            // If the namespace of the document is `MyComponents.Components.Shared`,
            // then the types `MyComponents.FooComponent`, `MyComponents.Components.BarComponent`, `MyComponents.Components.Shared.BazComponent` are all in scope.
            // Whereas `MyComponents.SomethingElse.OtherComponent` is not in scope.
            internal static bool IsTypeInScope(TagHelperDescriptor descriptor, string currentNamespace)
            {
                if (!TrySplitNamespaceAndType(descriptor, out var typeNamespace, out _) || typeNamespace.IsEmpty)
                {
                    // Either the typeName is not the full type name or this type is at the top level.
                    return true;
                }

                return IsTypeInScopeCore(currentNamespace, typeNamespace);
            }

            // Check if the given type is already in scope given the namespace of the current document.
            // E.g,
            // If the namespace of the document is `MyComponents.Components.Shared`,
            // then the types `MyComponents.FooComponent`, `MyComponents.Components.BarComponent`, `MyComponents.Components.Shared.BazComponent` are all in scope.
            // Whereas `MyComponents.SomethingElse.OtherComponent` is not in scope.
            internal static bool IsTypeInScope(StringSegment typeName, string currentNamespace)
            {
                if (!TrySplitNamespaceAndType(typeName, out var typeNamespace, out _) || typeNamespace.IsEmpty)
                {
                    // Either the typeName is not the full type name or this type is at the top level.
                    return true;
                }

                return IsTypeInScopeCore(currentNamespace, typeNamespace);
            }

            private static bool IsTypeInScopeCore(string currentNamespace, StringSegment typeNamespace)
            {
                if (!new StringSegment(currentNamespace).StartsWith(typeNamespace, StringComparison.Ordinal))
                {
                    // typeName: MyComponents.Shared.SomeCoolNamespace
                    // currentNamespace: MyComponents.Shared
                    return false;
                }

                if (typeNamespace.Length > currentNamespace.Length && typeNamespace[currentNamespace.Length] != '.')
                {
                    // typeName: MyComponents.SharedFoo
                    // currentNamespace: MyComponent.Shared
                    return false;
                }

                return true;
            }

            // We need to filter out the duplicate tag helper descriptors that come from the
            // open file in the editor. We mangle the class name for its generated code, so using that here to filter these out.
            internal static bool IsTagHelperFromMangledClass(TagHelperDescriptor tagHelper)
            {
                StringSegment className;
                if (tagHelper.IsChildContentTagHelper())
                {
                    // If this is a child content tag helper, we want to look at it's original type.
                    // E.g, if the type name is `Test.__generated__MyComponent.ChildContent`, we want to look at `Test.__generated__MyComponent`.
                    TrySplitNamespaceAndType(tagHelper, out var typeNamespace);
                    return TrySplitNamespaceAndType(typeNamespace, out var _, out className)
                        && ComponentMetadata.IsMangledClass(className);
                }

                return TrySplitNamespaceAndType(tagHelper, out var _, out className) &&
                    ComponentMetadata.IsMangledClass(className);
            }

            internal static bool TrySplitNamespaceAndType(TagHelperDescriptor tagHelperDescriptor, out StringSegment @namespace)
                => TrySplitNamespaceAndType(tagHelperDescriptor, out @namespace, out _);

            internal static bool TrySplitNamespaceAndType(TagHelperDescriptor tagHelperDescriptor, out StringSegment @namespace, out StringSegment typeName)
            {
                if (tagHelperDescriptor.ParsedTypeInfo is { } value)
                {
                    @namespace = value.Namespace;
                    typeName = value.TypeName;
                    return value.Success;
                }

                var success = TrySplitNamespaceAndType(tagHelperDescriptor.GetTypeName(), out @namespace, out typeName);
                tagHelperDescriptor.ParsedTypeInfo = new(success, @namespace, typeName);
                return success;
            }

            // Internal for testing.
            internal static bool TrySplitNamespaceAndType(StringSegment fullTypeName, out StringSegment @namespace, out StringSegment typeName)
            {
                @namespace = StringSegment.Empty;
                typeName = StringSegment.Empty;

                if (fullTypeName.IsEmpty)
                {
                    return false;
                }

                var nestingLevel = 0;
                var splitLocation = -1;
                for (var i = fullTypeName.Length - 1; i >= 0; i--)
                {
                    var c = fullTypeName[i];
                    if (c == Type.Delimiter && nestingLevel == 0)
                    {
                        splitLocation = i;
                        break;
                    }
                    else if (c == '>')
                    {
                        nestingLevel++;
                    }
                    else if (c == '<')
                    {
                        nestingLevel--;
                    }
                }

                if (splitLocation == -1)
                {
                    typeName = fullTypeName;
                    return true;
                }

                @namespace = fullTypeName.Subsegment(0, splitLocation);

                var typeNameStartLocation = splitLocation + 1;
                if (typeNameStartLocation < fullTypeName.Length)
                {
                    typeName = fullTypeName.Subsegment(typeNameStartLocation, fullTypeName.Length - typeNameStartLocation);
                }

                return true;
            }
        }
    }
}
